Composite furnace roof construction



Aug. 7, 1956 R. P. HEUER COMPOSITE FURNACE ROOF' CONSTRUCTION Filed Aug. 14. 1952 2 Sheets-Sheet 2 W \\U \\\\\m INVENTOR zzs'e? /arce Heuer ATTORNEYS.

United States Patent 2,757,623 Y CoMrosITE FUnNAcE Roon CONSTRUCTION Russell Pearce Heuer, Villanova, Pa., assignor to General. Refractories Company, a corporation of Pennsylvanta Application August 14, i952, serial No. 304,347

4 claims. (ci. 11o-99) The present invention relates to refractory roofs of the character employed in metallurgical furnaces such as open hearth steel furnaces and copper refining furnaces.

A purpose of the invention is to increase the life of the so-called zebra roof which has acid and basic refractory brick in alternating areas.

A further purpose is to improve the cooling effect on the roof by heat conduction through the refractory.

A further purpose is to employ refractory of higher heat conductivity to form refractory ribs at the cold surface of the roof.

A further purpose is to use comparatively short acid brick to obtain immediate cooling in the initial operation of the roof, and then to fill in the space between the areas of basic brick at the cold end by filler brick, which will be either acid or basic as preferred, when the acid brick wear away and become excessively thin.

A further purpose is to incorporate in a zebra roof auxiliary skewbacks suitable for supporting the'above described filler brick in whole or in part.

A further purpose is to support the filler brick by suspending them from the overhead structure or from the basic brick.

Further purposes appear in the specifications and in the claims.

In the drawings I have chosen to illustrate several of the numerous embodiments in which my invention may appear, selecting the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure l is a fragmentary diagrammatic section in the direction of the arc of the arch through the furnace roof of the invention.

Figure 2 is a fragmentary section on the line 2 2 of Figure 1, showing the roof as first installed.

Figure 3 is a section similar to Figure 2, showing the roof after it has been in service for a considerable length of time.

Figure 4 is a view similar to Figure 3 showing the roof after insertion of filler brick.

Figure 5 is a diagrammatic section in the direction. of an arch showing one form of roof to which the invention has been applied, sectioned on the line 5-5 of Figure 7.

Figure 6 is a fragmentary view similar to Figure 5 showing the roof after filler brick has been inserted.

Figure 7 is a top plan view of the roof of Figure 5.

Figure 8 is a fragmentary section of the roof of Figure 7 on the line 3 8.

Figure 9 is a View corresponding to Figure 4 showing the variation.

Figure 10 is a perspective of one of the initial basic brick employed in the preferred embodiment of the invention.

Figure ll is a perspective of one of the initial acid brick interposed between lthe basic brick in the invention.

Describing in illustration but not in limitation and referring tothe drawings:

. Wide use has been made in the prior art of the so- 2,757,623 Patented Aug. 7, 1956 called zebra roof, which has acid and basic brick courses alternating, and which has generally been applied to localized areas of the roof where premature failure occurs, e. g. over the back wall The basic brick at the hot face slags out less quickly than the conventional acid brick and after service the basic brick stick out at the hot face in ribs giving a striped appearance to the roof when viewed from inside the furnace. This has caused the zebra name. The projecting basic brick protect the silica brick and lengthen the roof life. The reason for longer roof life may be due in part to minimized contact of the acid brick with corrosive dusts carried by the furnace gases.

I have discovered that the life of a metallurgical furnace roof can be considerably increased by changing the zebra construction.

In accordance with the present invention, relatively long basic refractory brick are employed in spaced courses interposed by relatively short acid refractory brick. The basic refractory brick stick out to form cooling ns or ribs at the cold end, and after a short period of service they stick out also at the hot end. This construction has several advantages over the construction previously used: i

l. The basic refractory brick are more refractory than the acid refractory brick, and therefore if they attain a relatively higher temperature at the hot face they can nevertheless better withstand it.

2. The heat conductivity of the basic refractory brick is higher than that of the acid refractory brick and therefore the basic refractory brick are more effective to cool the hot face of those sections of the roof which may fail prematurely due to local overheating.

3. The basic refractory brick lend themselves well to inclusion of longitudinally extending oxidizable metallic plates which may be employed either on the surface, or running longitudinally in the interior or at both places. These plates are converted to oxide near the hot end but the portion toward the cold end remains in the form of metal and is very effective for the purpose of cooling the roof in locally overheated sections.

I prefer to use a single course of acid refractory brick between each course of basic refractory brick to make the coolingy action as effective as possible, although it will be understood that multiple course of acid or basic refractory brick may be interposed if desired.

The basic refractory brick are placed in courses, which are suitably arcwise of the arch. The bricks used may be 18 inches long, 6 inches wide at the top and somewhat less at the bottom as may be required by the arc to be formed, and 3 inches in thickness. The interspersed acid brick may be l2 inches long, 6 inches wide at the top (and tapering) and 3 inches thick. One course of silica will desirably be placed between each course of basic brick. Other suitable dimensions may be chosen.

After the acid refractory brick has worn away at the slower rate attributable to the improved cooling on account of its increased thinness, and on account of the cooling effect of the basic refractory brick, sufficiently to require repair, I insert filler brick at the cold end of the acid refractory brick between the basic refractory brick which stick out beyond. While the filler brick may extend over the entire furnace, they will preferably be applied only as required at hot spots and the like, and will preferably be supported either by special skewbacks built in the roof or by suspending the filler brick individually from the basic refractory brick. Thus by judicious repair of points where abnormal wear occurs, the life of the entire furnace is increased.

Considering the construction of Figures l to 4 inclusive, basic refractory brick 20 of relatively great length extend in the direction of the arc of the arch in spaced relation. The basic refractory brick 20 are suitably of chromite, magnesia or mixtures of chromite and magnesia in any proportions, and as best seen in Figure have on opposed faces, suitably the transverse faces 21, oxidiz able metallic plates 22, suitably of steel thoughpermissibly of aluminum alloy or copper alloy where the furnace temperature is low enough. The brick as shown has a cold end 26 and a hot end 27.

Interposed between each course of basic refractory brick is a course of acid refractory brick 28 suitably of silica. The acid refractory brick are shorter than the basic refractory brick so that the basic refractory brick stick up at 30 between the acid refractory brick courses when the furnace is initially constructed.

The brick courses in this form are supported by skewbacks 31.

In operation of the construction as shown in Figure 2 when first installed, it will be evident that the thinness of the acid refractory brick tends to keep them cooler than they otherwise would bc, so that they deteriorate initially at a reduced rate as compared with the prior art practice. At the same time the basic refractory brick cool the zebra roof section more effectively than previously was the case because of the inherently greater heat conductivity and because of the oxidizable metallic plates which run longitudinally of the basic refractory brick and contribute to the cooling especially near the cold end where they are not converted to oxide. At the same time the basic refractory brick, being more refractory, are less damaged by the interference with their cooling due to their increased length. Also the portion of the basic refractory brick sticking out at the cold end functions like a fin to aid heat transfer, and by heat conductivity through the hangers, the overhead supporting structure aids heat transfer to the air.

Figure 3 shows the structure after it has undergone considerable service. The hot face 32 of the acid refractory brick 28 has slagged and erroded away, making the basic refractory brick stick out at the hot face at 33. At the same time the acid refractory brick have become more effective in cooling because of their increased thinness. All this time the refractory brick continue to be supported by the skewbacks 31.

When the acid refractory brick 28 become dangerously thin particularly at the socalled hot spots of the furnace, filler brick 34 of the same transverse dimensions as the acid refractory brick are inserted against and beyond the cold face 35 of the acid refractory brick between the courses of basic refractory brick. The filler brick may be either acid refractory brick or basic refractory brick A and either character of filler brick will be preferable depending on the installation.

The zebra construction is generally applied in the section adjoining the backwall because this part wears most rapidly. The section over the front wall may also be of r zebra construction. This is shown in Figures 5 to 8. The middle section may be entirely silica and constructed of wedge brick 36 perhaps l5'l x 6" x 3" with rib brick 37 perhaps 20'I x 6" x 3" in alternate courses. I propose to build auxiliary skews into the roof where the zebra stops and elsewhere if necessary. Such skewback brick 38 are provided where the zebra sections 40 join the wholly silica central section 41 at the center. They may be shaped like brick 37, extending out as far as the basic brick 20 at the cold face, and will be of any suitable material, preferably of silica although perrnissibly of basic brick of the character described. The purpose of these auxiliary skews is to afford support for the filler brick 34 as shown in Figure 6. It is obvious that filler brick need not cover the entire roof area and the fillers are installed only where needed to keep the roof in operation. When laying the filler brick suitable mortar or cement may be used to get good brick contact.

Although I have indicated the use of zebra construction above the backwall because this area by virtue of local overheating and/ or excessive contact with dust laden gases gives the shortest roof life, the zebra can be applied to any part of the roof and may even extend across the entire width of the roof where service conditions so require. In such extended sections it may be desirable to mechanically support the basic ribs using any of the conventional methods of suspension.

In some cases especially where a very few filler brick are to be introduced, the filler brick may preferably be individually suspended. In Figure 9 I show a filler brick 34' which has metallic hangers 42 of L-section which are imbedded in the filler brick at the opposite sides of the cold end by comolding and extend out and hook at 43 over the top of the basic refractory brick courses.

The form of Figure l0 also shows metallic (steel) plates 44 which extend longitudinally through the interior of the basic brick and are imbedded in there by comolding. The plates 44 extend over the major portion of the length and width of the brick. This subject matter is embodied in my copending application Serial No. 301,942, filed July 3l, 1952, for Refractory Roof. The plates are omitted in the other figures, although they will very desirably be used on all of the basic brick. The plates will suitably be between l/ and V4 inch in thickness.

It will be evident of course that the invention finds its best application in furnaces operating at relatively high temperatures and presenting a severe refractory problem such as open hearth steel furnaces, although the invention is also applicable in furnaces of other types.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the method and structure shown, and I, therefore claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A refractory roof of curved arch form comprising courses of relatively long basic refractory brick, single courses of relatively short acid refractory brick interposed between and against the courses of basic refractory brick and being disposed closer to the hot ends than to the cold ends of said basic refractory brick the acid refractory brick being key-shaped, with the major axes extending in a radial direction and the principal minor axes extending transversely across the roof, the basic refractory brick extending straight out to their cold ends beyond the cold ends of the acid refractory brick, and single courses of key-shaped filler brick between and against the courses of basic refractory brick at the cold ends of the acid refractory brick, the fller brick having their major axes radial and their principal minor axes extending transversely across the roof.

2. A refractory roof according to claim l, in which the filler brick have hangers providing support and engaging the basic refractory brick.

3. A refractory roof according to claim l, in which the filler brick are acid.

4. A refractory roof according to claim l, in which the ller brick are basic.

References Cited in the fle of this patent UNITED STATES PATENTS 1,095,920 Orth May 5, 1914 1,709,350 Jackman Apr. 16, 1929 2,085,837 Thomas July 6, 1937 2,236,920 Robertson Apr. l, 1941 2,304,170 Heuer Dec. 8, 1942 FOREIGN PATENTS 592,091 Germany Feb. 1, 1934 807,010 France Oct. 5, 1936 611,704 Great Britain Noll. 3. 1948 

1. A REFRACTORY ROOF OF CURVED ARCH FORM COMPRISING COURSES OF RELATIVELY LONG BASIC REFRACTORY BRICK, SINGLE COURSES OF RELATIVELY SHORT ACID REFRACTORY BRICK INTERPOSED BETWEEN AND AGAINST THE COURSES OF BASIC REFRACTORY BRICK AND BEING DISPOSED CLOSER TO THE HOT ENDS THAN TO THE COLD ENDS OF SAID BASIC REFRACTORY BRICK THE ACID REFRACTORY BRICK BEING KEY-SHAPED, WITH THE MAJOR AXIS EXTENDING IN A RADICAL DIRECTION AND THE PRINCIPAL MINOR AXES EXTENDING TRANSVERSELY ACROSS THE ROOF, THE BASIC REFRACTORY BRICK EXTENDING STRAIGHT OUT TO THEIR COLD ENDS BEYOUND THE COLD ENDS OF THE ACID REFRACTORY BRICK, AND SINGLE COURSES OF KEY-SHAPED FILLER BRICK BETWEEN AND AGAINST THE COURSES OF BASIC REFRACTORY BRICK AT THE COLD ENDS OF THE ACID REFRACTORY BRICK, THE FILLER BRICK HAVING THEIR MAJOR AXES RADIAL AND THEIR PRINCIPAL MINOR AXES EXTENDING TRANSVERSELY ACROSS THE ROOF. 